Heat recoverable article

ABSTRACT

A resiliently flexible ring of dimensionally heat-recoverable polymeric material whose tubular length is less than its notional circular diameter, formed so that it inherently maintains a non-circular open configuration enabling it to grip resiliently an object around which it is placed in use prior to heat-recovery, the maximum transverse dimension of the said object being at least 2.5% less, preferably at least 5% less, than the notional circular diameter of the ring. The ring preferably has at least three &#34;corners&#34; of relatively small radius of curvature, preferably evenly spaced around its circumference. Use of the rings is described for damping the noise of chain-drive sprocket wheels and for connecting flexible hoses to supply outlets.

This invention relates to dimensionally heat-recoverable polymericarticles, such articles made, for example, of cross-linked polyolefinplastics, being generally well known. Methods and materials for makingsuch articles have been described, for example, in U.S. Pat. Nos.3,086,242 and 3,597,372.

SUMMARY OF THE INVENTION

The present invention provides a special form of such article, which isparticularly convenient to use in certain situations. The inventionaccordingly provides a resiliently flexible ring of dimensionallyheat-recoverable polymeric material formed so that it inherentlymaintains a non-circular open configuration enabling it to gripresiliently an object around which it is placed in use prior toheat-recovery, the maximum transverse dimension of the said object beingat least 2.5% less, preferably at least 5% less, than the notionalcircular diameter of the ring.

References herein to a "ring" will be understood to mean open-endedtubular articles whose length is less than their notional circulardiameter (the length of their perimeter divided by pi). The invention isespecially advantageous with rings whose length is less than half, orless than one quarter, or less than one eighth, of their notionalcircular diameter.

By providing such a ring in non-circular open configuration, theinvention ingeniously enables the ring to grip a circular object, aboutwhich such rings may be fitted, prior to heat recovery to shrink thering tightly onto the object. The open configuration enables the ring tobe fitted onto the object without difficulty, unlike a flattened tubularconfiguration which would be difficult to hold open during fitting.However, the resilient grip provided by the non-circular configurationaccording to the present invention reduces the irritating problem of thering falling off the object between the initial fitting and theheat-recovery operation. This problem is more severe with axiallyshorter rings especially those whose tubular or axial length is lessthan one eighth of their notional circular diameter, when applying themclose to the end of objects such as shafts or hoses. One particularlyrelevant case is that in which the length of an object available toreceive a short ring is little greater than, or equal to, the shorttubular length of the ring.

The non-circular open configuration of the ring according to thisinvention could be simply eliptical having two equal "ends" ofrelatively small radius of curvature, or possibly pear-shaped having onesmaller and one larger "end". However, it is preferred to provide thering with at least three "corners" of relatively small radius ofcurvature (relative to the notional circular diameter), preferablyevenly spaced around its circumference. The longer portions of the ringextending between these corners may be curved with a larger radius thanthe corners, or may be substantially straight, giving the ring atriangular, square, pentagonal, or hexagonal configuration, depending onthe number of corners provided. It will be realised that the usefulnessof the gripping effect will diminish as the number of corners increasesbeyond about six, and it is thought that fewer than ten, preferablyfewer than eight, corners will be desirable in most cases. Three or fourcorners, most preferably three, will tend to give a more positive gripfor locating the ring on a round object. The radius of curvature of the"corners" will preferably be less than 1/4, more preferably less thanone eighth, and especially preferably less than one tenth or less thanone twentieth, of the notional circular diameter of the ring.Sharp-pointed corners are not excluded, but are likely to be lessconvenient in practice. Rounded corners are preferred.

The rings according to the invention may be made by known techniques,for example by individual moulding, or by extrusion of a tube which iscut to length. The non-circular open configuration will preferably beimparted after the moulding or extrusion of a substantially circularshape, for example during the usual hot expansion process which is usedto convert the article into its heat-recoverable expanded state.Stretching on an array of mutually separable circular pins will produceone "corner" per pin, with the radius of curvature determined by theradius of the pins.

Suitably non-brittle materials for making the rings may be selected fromthose known for making heat-recoverable articles, provided that anadequate degree of resilient flexibility is present. With that proviso,any polymeric material which can be cross-linked and to which theproperty of dimensional recoverability may be imparted, such as thosedisclosed in U.S. Pat. No. 3,086,242, may be used to form the rings.Preferred materials include: polyolefins, e.g. low, medium or highdensity polyethylene; polypropylene; ethylene copolymers, e.g. withalpha olefins such as propylene, 1-butene, 1-hexene or 1-octene, orvinyl acetate or other vinyl esters or methyl or ethyl acrylate;polyamides, especially Nylon materials, e.g. Nylon 6, Nylon 6,6, Nylon11 or Nylon 12 or those disclosed in U.S. Pat. No. 4,444,816; orpolyurethanes. The disclosures of the above patent specifications areincorporated herein by reference. Materials which are at least to someextent elastomeric may be preferable for some end uses. The material ispreferably cross-linked in known manner by chemical cross-linking agentsand/or by exposure to high energy radiation.

Preferred materials, especially for accoustic damping applications, aredescribed in U.S. Pat. No. 4,860,851, the disclosure of which isincorporated herein by reference.

The invention also provides a method of applying a ring ofheat-recoverable material to an object, comprising positioning on theobject a ring according to the present invention of such a size that itresiliently grips the object, followed by heating to recover the ringtightly onto the object. The object will have a maximum transversedimension (i.e. transverse to the tubular axis of the ring) at least2.5%, preferably at least 5%, less than the notional circular diameterof the ring. Preferably the ring will be large enough to enable it to beeasily flexed and slipped onto the object, after which its resiliencewill cause it to grip the object at at least two points of contacttherewith while awaiting heat recovery to shrink it tightly onto theobject. Before recovery the ring will not touch the object at all pointsof its perimeter, preferably touching it at fewer than ten points over atotal contact length less than half, or less than 1/4, or less than 1/10of the ring perimeter. The object is preferably substantially round incross-section, for example a round shaft or pin or projection, or a hoseand its diameter is less than the notional circular diameter asaforesaid.

The invention is especially useful in a method of drive chain noisedamping wherein the said object to which the ring is applied is aportion of a chain sprocket wheel projecting to the side of the plane ofrotation of the sprocket teeth, and the ring is of sufficient thicknessand resilience to damp the chain noise.

The invention is also especially useful in applying the recoverablerings at or near the ends of flexible hoses, for example vehicle heatinghoses or domestic appliance hoses, in order to secure the hoses toco-operating fittings during assembly. The invention includes laterallyconnected sets of two or more of the rings, for example for the purposeof securing together two or more hoses or other objects. The lateralconnection is preferably formed by a web of the ring material.

DESCRIPTION OF THE DRAWINGS

The aforementioned chain-drive-damping embodiment of the invention willnow be described in more detail by way of example, with reference to theaccompanying schematic drawings, wherein:

FIG. 1 shows in perspective a three-cornered ring of dimensionallyheat-recoverable material according to the present invention;

FIG. 2 shows a side view of a chain drive sprocket wheel with the ringof FIG. 1 gently gripping a circular projecting portion of the sprocketwheel before heat recovery;

FIG. 3 shows as end view in section on the lines 3--3 of FIG. 2; and

FIGS. 4 and 5 show the arrangement of FIGS. 2 and 3 respectively afterheat recovery of two rings onto the sprocket wheel and engagement of adrive chain around the wheel.

Referring to the drawings, the three-cornered ring 1 shown in FIG. 1 ismade of hydrogenated nitrile rubber, carbon black and a polyesterelastomer as described in the aforementioned U.S. Pat. No. 4,860,851,and has a tubular length L which is less than 1/8 of its notionalcircular diameter indicated by line NCD.

In FIGS. 2 and 3, the ring 1 has been positioned on laterally projectingcircular portion 3 of a sprocket wheel 2 immediately adjacent to thesprocket teeth 4. The diameter d of the projecting portion 3 is about1/3 less than the NCD of ring 1, which is therefore easily flexed andslipped over the portion 3. The ring 1 thereafter gently grips theportion 3 by contact at about the mid-point of its three sides, the sizeof the ring naturally having been selected to achieve this effect.

After recovery of two rings 1 onto the projecting sprocket wheelportions 3, as shown in FIGS. 4 and 5, a drive chain 5 may be engagedwith the sprocket teeth 4. As shown most clearly in partialcross-section in FIG. 5, the chain 5 has connecting pins 6 flexiblyjoining links 7 and 7', parts of which link 7 come into contact with theouter surface of the shrunk rings 1, thereby damping the chain noise.The rings thus provide a very convenient replacement for knownmoulded-on rubber damping structures.

The use of the rings on flexible hoses will now be described by way ofexamples with reference to FIGS. 6 and 7 of the accompanying schematicdrawings, wherein:

FIG. 6 shows in perspective a hexagonal ring in position near the end ofa hose prior to fitting of the hose into a supply spigot; and

FIG. 7 shows in cross-section a joined pair of rings positioned on theends of a pair of hoses.

In FIG. 6, the ring 10 has been expanded with six "corners" andresiliently grips the hose 11 near its end. The hose can be fitted overthe supply spigot 12 (or other member insertable into the hose), e.g. awater valve outlet, and the ring 10 can then be recovered by heating toclamp the hose 11 to the spigot 12.

In FIG. 7, the two rings 20 are joined together laterally (that is bytheir outer surfaces) by a web 21 and are shown in position on a pair ofhoses 22. The ring shown on the right has been heat recovered about itshose, while the ring shown on the left is resiliently gripping its hoseprior to being recovered.

We claim:
 1. A hose coupling article comprising a resiliently flexiblering of dimensionally heat recoverable polymeric material whose tubularlength is less than its notional circular diameter, formed so that itinherently maintains a non-circular open configuration enabling it togrip resiliently an object around which it is placed in use prior toheat recovery, the maximum transverse dimension of the said object beingat least 2.5% less than the notional circular diameter of the ring andthe ring being laterally connected to at least one other such ring sothat the connected rings are capable of securing together at least twoflexible hoses.
 2. An article according to claim 1, whose tubular lengthis less than half of its notional circular diameter.
 3. An articleaccording to claim 2, whose length is less than one quarter of itsnotional circular diameter.
 4. An article according to claim 2, whoselength is less than one eighth of its notional circular diameter.
 5. Anarticle according to claim 1, whose configuration is elliptical.
 6. Anarticle according to claim 1, whose configuration is pear-shaped.
 7. Anarticle according to claim 1, having at least three corners whose radiusof curvature is less than one quarter of the said notional circulardiameter.
 8. An article according to claim 7, having from four to sixsuch corners.
 9. An article according to claim 7, having three suchcorners.
 10. A method of securing together two or more flexible hoses,comprising positioning the laterally connected rings according to claim1 respectively onto the separate hoses, followed by heat recovery of therings tightly onto the hoses.
 11. A method according to claim 10,wherein the hoses are substantially round in cross-section and theirdiameter is at least 2.5% less than the said notional circular diameterof the rings.